1. Field of the Invention
The present invention is related to a die-protecting device used in bending an embossed metallic straight pipe with a small diameter and a thin wall and having an artistic embossed pattern thereon. The device is comprised of a plastic die core for put in the straight pipe; a pair of half-dies are put on and envelop the straight pipe. A plastic pipe is slipped over the half-dies, then a spiral spring is slipped over the plastic pipe, and further a tension spring is slipped over the spiral spring. Both open ends of the tension spring are provided with a sealing cover. The die-protecting device formed is used for bending the embossed metallic straight pipe with a small diameter and a thin wall and having an artistic embossed pattern thereon. The device has a function of scattering the bending stress on the pipe wall, and thus has a protection effect preventing the pipe wall from collapsing during bending forming.
2. Description of the Prior Art
In conventional techniques of bending a metallic straight pipe used in the art, the most convenient method is to place the metallic straight pipe on a bending machine to bend and make modeling with mechanic arms. Such method has been widely used in pipe connection operation of steel pipes (such as iron gas pipes, water pipes etc.). However until now, it is not that all the metallic pipes suit bending and modeling on bending machines, their pipe bodies must have enough thickness and stiffness to be processed by bending and modeling without deformation. For example, aluminum or copper pipes made of non-ferrous alloy do not suit bending and modeling on bending machines. This is because the metallic pipes of such material have inferior stiffness than that of steel alloy, and is subjected to overly large stress concentration in the pipes. And more, no matter what material the metallic pipes are made of, if their diameters are too small and their walls are too thin, difficulty in bending operation will be increased relatively. This has not mentioned the metallic pipes with small diameters and thin walls having artistic embossed pattern thereon (they are called embossed metallic pipes in the present invention) which are even larger in difficulty. There has not yet had a technique in the art to use a more easily operated bending machine to proceed bending operation on such pipes, because it is difficult to practice. Thereby, it is a bottleneck hard to overcome in raising bending techniques toward delicate artistic modeling of the pipe articles (metallic pipes). Delicate articles such as metallic rails, table legs, chair legs or show shelves etc. with small diameters and thin walls and having artistic embossed patterns thereon are hard to process by bending when they have been made straight embossed pipes and are desired to be bent.